The MedSea Cruise was conducted during May 2013 and covered the whole Mediterranean basin, allowing a wide picture about the presence and distribution of Mediterranean gelatinous zooplankton.
Samples were collected using three different nets (Bongo net, Neustonic net and Mocness net) and a motor pump system (for plankton collection) in all the sampling points, aiming to study the distribution and fulfil different analysis to understand their role in the ecosystem.
The gelatinous zooplankton composition differed between the Eastern and the Western Mediterranean. In the Eastern Mediterranean from Lebanon to Messina strait, the most common gelatinous animals were salps. Although they were present in almost everywhere east of Messina, several aggregations were found in some areas like the north Adriatic Sea and the Otranto strait. Chaetognaths were also present and the size of the specimens was surprisingly big. In addition to salps, the surface-dwelling hydromedusa Porpita porpita was seen in almost all the stations, and specimens of this species were collected with the neustonic net and separated for different analyses. Moreover, one of the most abundant scyphozoans in the Mediterranean, Pelagia noctiluca, was observed sporadically in few numbers.
In the Western Mediterranean, west of the Messina strait, the gelatinous zooplankton composition, as well as the rest of the plankton community, was different from the east. Plankton abundance also was higher in the western area. Porpita porpita was not observed, while Velella velella, a similar Mediterranean hydromedusa was abundant and often present in the samples.
Almost at the end of the cruise, closer to Barcelona in the Alguero-Balearic Basin and in the Catalan- Balearic Sea, differences were observed in the samples collected during day and night. During the day, the samples contained Velella velella in high abundances, while during the night, only Pelagia noctiluca was collected in high numbers.
Although some difficulties occurred in the last part of the cruise due to bad weather, almost everything that was planned was successfully completed. Overall, it was a fascinating and really fruitful cruise for the “MEDUSA” group of Barcelona and the European projects involved.
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